Apparatus for assembling and winding a strip about lead wires

ABSTRACT

An apparatus for forming a miniature capacitor from a single strip of dielectric material metalized on each of its sides is disclosed. The strip passes from a supply reel over a guide roller and along a feed chute to a winding station, where it is initially located between the first lead wire and a retractable winding pin located adjacent an elongated slot. The strip then proceeds to a take-up block in a guide chute. The winding pin orbits so as to carry the strip around the first lead wire in the form of a loop which is wound into the capacitor after the second lead wire has been inserted. The first lead wire is loaded in an axial direction at one end of the slot and carried to the other end of the slot by the looped strip as the strip is carried around the lead wire by the orbiting of the winding pin and slot. The second lead wire is then fed into the slot along the same axis as the first lead wire was fed, and the winding pin is retracted, without any interruption in the winding. The leads are then retained in the capacitor by heat shrinking the dielectric strip.

United States Patent [1 1 Rayburn Jan. 29, 11974 APPARATUS FOR ASSEMBLING AND WINDING A STRIP ABOUT LEAD WIRES Primary Examiner'Ihomas l-l. Eager [75] Inventor: Charles C. Rayburn, Glenview, Ill. 57] ABSTRACT Asslgneei Illinois Tool Works Inc, Chicago, An apparatus for forming a miniature capacitor from a single strip of dielectric material metalized on each of 2 Filed; 30, 1972 its sides is disclosed. The strip passes from a supply Appl. No.: 284,855

Related US. Application Data reel over a guide roller and along a feed chute to a winding station, where it is initially located between the first lead wire and a retractable winding pin located adjacent an elongated slot. The strip then proceeds to a take-up block in a guide chute. The winding pin orbits so as to carry the strip around the first lead wire in the form of a loop which is wound into the capacitor after the second lead wire has been inserted. The first lead wire is loaded in an axial direction at one end of the slot and carried to the other end of the slot by the looped strip as the strip is carried around the lead Wire by the orbiting of the winding pin and slot. The second lead wire is then fed into the slot along the same axis as the first lead wire was fed, and the winding pin is retracted, without any interruption in the winding. The leads are then retained in the capacitor by heat shrinking the dielectric strip.

4 Claims, 15 Drawing Figures PATENTEI] JAN 2 91974 SHEET 2 0F 2 APPARATUS FOR ASSEMBLING AND WINDING A STRIP ABOUT LEAD WIRES This is a division, of application Ser. No. 4,386,'filed Jan. 20, 1970, U.S. Pat. No. 3,576,481, and application Ser. No. 104,887, filed Jan. 8, 1971, US. Pat. No. 3,715,784.

BACKGROUND OF THE INVENTION This invention relates to wound capacitors and particularly to an improved apparatus for manufacturing Capacitors folded on a line at their center and wound or wrapped from their centers about a mandrel, are known in the prior art as exemplified by US. Pat. Nos. 2,887,649 and 2,920,834. In each of these patents, the metallized coatings on the opposite sides of the dielectric strip are offset in a transverse direction so that leads may be attached to the ends of the capacitor. Although there are many instances in the prior art where it has been proposed to use the lead wires as at least one of the winding mandrels, such devices generally require secondary operations. For example, in US. Pat. No. 3,229,] 74 and German Pat. No. 886,634, the lead members must be attached by adhesive or welding to an electrode foil before winding. In US. Pat. No. 2,790,607, the winding takes place generally about a pair of wires but the wires are attached to the two separate metalized strips forming the capacitor by means of a thermoplastic adhesive and are, in the principal embodiment of the invention, designed to be removed after winding. Although the last named patent contemplates the possibility of leaving one of the wires in the capacitor for use as a lead wire, it is not possible to use both of the wires in this manner.

The main object of the invention is to provide a winding apparatus wherein only a single supply roll of metalized dielectric and a single spool of lead wire is required.

The object is obtained by theapparatus of the present invention wherein the capacitor is formed by winding a single strip of two-side metalized dielectric material about two straight wires which act as mandrels but remain in place to function as lead wire connections. The strip of metalized dielectric material has unmetalized margins on each edge of both sides and, in a preferred embodiment of assembly apparatus, is wound initially with a portion intermediate its ends positioned between a first lead wire and a retractable pin which is spaced from the first lead wire and of a greater diameter. The second lead wire is inserted and the retractable pin is withdrawn after a predetermined number of winding revolutions have taken place. During the initial revolutions the retractable pin orbits around the first lead wire together with a loop of strip material which it forms. Since the pin and first lead wire are spaced from each other, the capacitor will initially be wound at a large effective diameter. Because of the loop, four thicknesses of material will be wound at one time. It can thus be readily appreciated that the capacitor will be wound quickly and with relatively few turns as compared to conventional capacitors. After the retractable pin has orbite'd so as to carry the loop of strip material around the first lead wire atleast once, the second lead wire is inserted so as to contact the side of the metal ized strip which is opposite to that contacted by the first lead wire. Following the insertion of the second lead wire, the retractable pin is withdrawn, the winding of the capacitor is completed, the strip is cut from its supply reel, and the ends of the strip are taped or otherwise sealed to hold the layers together. In an alternative embodiment, an intermediate portion of the strip is initially folded back on itself twice in zig zag fashion to form a three thickness portion which is then engaged on its opposite sides by a pair of lead wires. The strip is then wound using the lead wires as mandrels.

The improved method of winding causes a central portion of the dielectric strip to be folded at least twice and doubled back on itself, resulting in several layers of dielectric separating the leads of the capacitor and protecting ,them against arcing inside the winding. At the points where the leads egress from each end of the winding, they are spread apart after the winding is completed and the ends of the capacitor are sealed and filled with an insulation material such as epoxy resin in order to prevent arcing in that region, insulate the ends, lock the leads against translation or rotation, and protect the unit against the entry of moisture. It will be appreciated that the finished capacitor will be extremely compact since it does not contain the usual voids produced by removable winding mandrels. Since the leads are internally mounted, they are firmly anchored and offer good electrical contact since the metalized layers contact the major portion of their periphery.

Since the winding process causes a pair of lead wires to extend from each end of the capacitor, it is possible to selectively cut and form the lead wires so as to produce either axial, radial, or stand-up lead arrangements, although the structure is probably most useful in the stand-up style which is adapted to be mounted in printed circuit boards.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a front perspective schematic view of a simplified hand operated winding apparatus for winding capacitors in accordance with the process of the invention;

FIG. 1B is a fragmentary rear perspective schematic view of the device shown in FIG. 1A;

FIGS. 2-8 are schematic diagrams illustrating the relationships between the dielectric strip, the lead wires, and the retractable winding pin at various stages during the winding of a capacitor;

FIG. 9 is a plan view of a capacitor showing the relationship of the lead wires to each other immediately after winding;

FIG. 10 is a view similar to FIG. 9 showing the lead wires after they are spread apart from each other;

FIG. 11 illustrates the capacitor of FIG. 10 after the leads at one end have been cut off and the leads at the other end have been formed;

FIG. 12 is a view similar to FIG. 11 but wherein an insulating coating has been applied to the ends of the wound strip; 8

FIG. 13 is a schematic diagram of a modified form of winding apparatus; and

FIG. 14 is a transverse cross-sectional view of a capacitor made in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1A and 1B, a simple hand operated apparatus for winding the capacitor of the invention is shown. The apparatus includes a frame 10 supporting a supply reel 12 of heat shrinkabledielectric material such as polyester or polypropylene film coated on each of its first and second sides with metalized coatings and 15' which form the two electrodes of the finished capacitor. The coatings 15, 15' are spaced from each of the strip edges by unmetalized margin regions. The dielectric strip 14 passes from the supply reel 12 over a guide roller 16, along a feed chute 17 and through a winding station indicated generally at 18 to a take-up block 20 to which it is attached during winding by a piece of adhesive tape 21. The take-up block 20 is mounted for reciprocating movement within take-up guide chute 22 and is manually movable by handle 24. A series of scale markings 26 are provided on the takeup guide chute 22 so that the take-up of block 20 can be moved, by means of its handle 24, to any desired predetermined position on the scale depending on the value of the capacitor being wound. Once the take-up block 20 is attached to the dielectric strip 14 by the ad hesive tape 21, it will remain in said predetermined position until winding commences if the tensions in the supply and take-up portions of the apparatus are properly balanced. The take-up tension is controlled by varying the size of tension weight 30 which is attached to the take-up block 20 by means of a cord 32 passing over pulleys 34, 36. The tension on the supply reel is controlled by adjusting the size of weight 40 acting on the cord 42 which passes over a hub or shoulder (not shown) on the back of supply reel 12 to cause a braking or dragging action on the supply reel 12. The various tensions can be readily adjusted and matched to each other so the strip 14 will remain stationary when at rest by removing or adding weights in accordance with the type of strip material used, the winding tension desired, and-the amount of material on the supply reel 12.

Prior to winding the strip 14 to form a capacitor, a first lead wire member 48 is inserted with its inner end in an elongated slot 50 in a winding head 52. The outer end of the lead wire 48 is supported in an outboard lead support 58 which is freely mounted for rotation on a lead support slide 60 which is in turn mounted forin and out movement relative to the frame plate 10 on a guide rail 62.

Once the first lead wire 48 is placed in slot 50 and support 58 and next to the strip 14, the drive shaft 66 may be rotated by handle 68 to cause rotation of the pulley 70, the belt 72, the pulley 74, and thus the winding head 52. Rotation of the winding head 52 in a clockwise direction about its center of rotation 49 will cause a winding pin 54 thereon having a diameter larger than the lead wires to carry the strip 14 in a loop 14' around the first lead wire 48 as shown in FIG. 3. After one rotation, the strip will assume the configuration shown in FIG. 4 wherein it can be seen that the first lead wire 48 has been pulled sideways to the end of slot 50 which is opposite to the center of rotation 49. Continued rotation of the winding head 52 one-half or more turns to the relative position shown in FIG. 5 will permit the second lead wire 75 to be inserted on the same axis 49 on which first lead wire 48 was originally placed. Since both lead wires are fed along the same axis, they can be cut from the same supply reel (not shown) or fed as short lengths. Inserting the second lead wire 75 in the middle of a revolution of the winding head 52 as shown in FIG. 5 will permit it to contact the second side metalized surface 15'. After the second lead wire 75 has been inserted, the winding pin 54 (see FIG. 6) may be rotated on its own shaft 76 in winding head 52 so winding pin 54 will move closer to slot 50. This movement is permitted by the fact that the winding pin 54 is eccentrically mounted. Rotation of eccentric shaft 76 so as to move winding pin 54 closer to the slot 50 will also move it out of contact with the loop 14' which it had formed in the strip 14. In this position where it is out of contact with the loop, the eccentric shaft can be axially retracted so as to withdraw the winding pin 54 and prevent its further contact with the strip 14. Once the winding pin 54 is retracted, continued rotation of the winding head 52 will cause the loop 14 to be wound into the body of the capacitor as seen in FIGS. 7 and 8.

It can be seen in FIG. 7 that lead 48 will contact metalized surface 15 along a first intermediate portion 14a on the strip 14 and that lead will contact surface 15 along a second intermediate portion 14b on the strip whichis spaced from portion 14a by a distance greater than twice the circumference of lead 48. This spacing insures that the leads are well insulated against shorts and also reduces the opportunity for damage to the dielectric strip 14 when soldering heat is applied to the leads 48, 75 of a finished capacitor since the heat may be dissipated over a large area.

When winding has proceeded to the point wherein take-up block 20 has been lifted by the strip 14 and adhesive tape 21 to the top of guide chute 22, the winding is stopped. At this time, a clamp 77 on a shaft 78 is rotated into clamping engagement with strip 14 and a razor blade or other cutting device used to sever the strip 14 at the lower edge 17' of the feed chute 17. The clamp 77 is normally biased by a spring 80 away from the feed chute, but may be held against the strip- 14 by means of the handle 82.

After the strip 14 is severed at the lower edge 17' of the feed chute and the adhesive tape 21 removed from the take-up block 20, the capacitor is rotated until the adhesive tape 21 has been pressed around the outside of the capacitor to hold its wraps together.

After the capacitor is wound and sealed by tape 21, it may be removed from the winding station 18 by sliding lead support slide .60 on guide rail 62 suifficiently far so as to release outboard lead support 58 from contact with the first and second lead wires 48 and 75. The capacitor is then withdrawn from slot 50.

In FIG. 9 the capacitor and its leads are shown in the relative positions they assume after the winding operation. FIG. 10 illustrates how the pairs of lead wires can be bent away from each other while FIG. 11 shows that the leads which have already been bent can be clipped at one end and formed at the other in such a manner that the capacitor can be utilized in a printed circuit board. If desired, by clipping appropriate leads, the capacitor could also be formed so as to have axial leads or radial leads. As seen in FIG. 12, the capacitor 12 can be insulated and sealed by injecting a filler material 86 such as epoxy resin in the ends thereof. This filler material not only seals the capacitor against moisture but also locks the leads firmly and prevents relative rotation of them and shorting.

FIG. 13 illustrates an alternative embodiment of the invention wherein a strip of dielectric material metalized on both sides may be placed in a zig zag doubled back fashion around a pair of loop forming pins 116, 118. A pair of first and second lead wire members 148 and are then brought into contact with the opposite sides of the strip and the pins 116,-118 withdrawn.

The capacitor is then wound by utilizing the lead wire members 148, 175 as winding mandrels.

FIG. 14 illustrates the cross-section of a finished capacitor 88 wherein the dielectric film has been heated to shrink it after bending the leads to the position shown in FIG. 10.

I claim:

1. Apparatus for winding a capacitor from a single strip of two side metalized dielectric comprising:

a supply reel for providing a continuous supply of.

said mctalized strip;

means for providing back tension on said supply reel;

a winding head including an elongated slot adapted to support a pair of lead wires; an auxiliarly winding pin mounted eccentrically in said winding head for axial movement into and out of the path of a strip to be wound and for radial movement relative to said slot; means for rotating said winding head; a slidable block adapted to be connected to the leading end of said strip prior to winding said strip; means for urging said slidable block away from said winding head; guide means for guiding said slidable block toward said winding head as said strip is wound from an intermediate portion thereof about said pair of lead wires. 2. The winding apparatus as defined in claim 1 wherein clamp means are provided for clamping said strip between said supply reel and said winding head at the completion of a winding operation to permit the wound portion of the strip to be severed from the supply.

3. The winding apparatus as defined in claim 2 wherein the axis of rotation of said winding head is at the end of said slot most remote from said auxiliary winding pin, said slot being adapted to receive the first of said pair of lead wires at said remote end, said slot being further adapted to permit said first lead wire to move transversely of its axis to the opposite end of the slot as a strip placed between said first lead wire and said auxiliary winding pin at the commencement of a winding operation is partially wound by rotation of said winding head, said movement of said first lead wire in said slot permitting the second lead wire to be received at the remote end of the slot and wound into contact with said strip by the rotation of said winding head, said auxiliary winding pin being axially withdrawn from contact with said strip after said second lead wire is received in said slot.

4. The winding apparatus as defined in claim 3 and further comprising means for supporting said pair of lead wires at their ends remote from said slot, said means for supporting serving to hold said lead wires in fixed position relative to each other while permitting their rotation during the winding of said strip thereon, said means for supporting being axially movable relative to said lead wires at the completion of a winding operation to permit the capacitor to be unloaded from the apparatus. 

1. Apparatus for winding a capacitor from a single strip of two side metalized dielectric comprising: a supply reel for providing a continuous supply of Said metalized strip; means for providing back tension on said supply reel; a winding head including an elongated slot adapted to support a pair of lead wires; an auxiliarly winding pin mounted eccentrically in said winding head for axial movement into and out of the path of a strip to be wound and for radial movement relative to said slot; means for rotating said winding head; a slidable block adapted to be connected to the leading end of said strip prior to winding said strip; means for urging said slidable block away from said winding head; guide means for guiding said slidable block toward said winding head as said strip is wound from an intermediate portion thereof about said pair of lead wires.
 2. The winding apparatus as defined in claim 1 wherein clamp means are provided for clamping said strip between said supply reel and said winding head at the completion of a winding operation to permit the wound portion of the strip to be severed from the supply.
 3. The winding apparatus as defined in claim 2 wherein the axis of rotation of said winding head is at the end of said slot most remote from said auxiliary winding pin, said slot being adapted to receive the first of said pair of lead wires at said remote end, said slot being further adapted to permit said first lead wire to move transversely of its axis to the opposite end of the slot as a strip placed between said first lead wire and said auxiliary winding pin at the commencement of a winding operation is partially wound by rotation of said winding head, said movement of said first lead wire in said slot permitting the second lead wire to be received at the remote end of the slot and wound into contact with said strip by the rotation of said winding head, said auxiliary winding pin being axially withdrawn from contact with said strip after said second lead wire is received in said slot.
 4. The winding apparatus as defined in claim 3 and further comprising means for supporting said pair of lead wires at their ends remote from said slot, said means for supporting serving to hold said lead wires in fixed position relative to each other while permitting their rotation during the winding of said strip thereon, said means for supporting being axially movable relative to said lead wires at the completion of a winding operation to permit the capacitor to be unloaded from the apparatus. 